The Universal Mobile Telecommunications System (UMTS) is a third-generation (3G) mobile phone technology standardized first by the European Telecommunications Standards Institute (ETSI) and now by the 3rd Generation Partnership Project (3GPP). UMTS carries both circuit switched (CS) and packet switched (PS) traffic using Wideband Code Division Multiple Access (W-CDMA) as its air interface. The description of the network components and protocols used in UMTS are well known to those of ordinary skill in the art and are available to the public from 3GPP, ETSI, and other sources. The UMTS network architecture consists of three domains: Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN), and User Equipment (UE).
The Core Network provides switching and routing for user traffic and provides network management functions. The Core Network architecture is based on the GSM network with GPRS. The UTRAN provides the air interface access to subscribers' UE. Base stations in the UTRAN are referred as Node-Bs, and the control equipment for the Node-Bs is called a Radio Network Controller (RNC). The UMTS User Equipment communicates via the WCDMA air interface to the Node-Bs. The UE may be attached to either the PS domain or CS domain or both. The UE is capable of simultaneously using PS services and CS services.
UMTS defines several interfaces and protocols for exchanging data between network components to set up voice and data calls to the UE. Each call comprises numerous messages that pass across various interfaces. In order to fully analyze a call, all of the messages for the call must be collected and correlated. One disadvantage of the prior art is that some data packets are encrypted and must be deciphered before they can be analyzed. For example, the Radio Resource Control (RRC) packets require a Ciphering Key (CK) to be deciphered. However, the CK is not available on the same interfaces that pass the RRC packets.
A second disadvantage of the prior art is that network monitoring equipment may be widely distributed to monitor a UMTS network. As a result, a monitor or probe that captures a CK may not be co-located with a monitor that captures an RRC packet that needs the CK to be deciphered.